docs: def format_iso_datetime(datetime_obj):
      """Formats the given datetime as a UTC-zoned ISO 8601 date string.
  
      :param datetime_obj: The datetime object.
      :type datetime_obj: datetime
      :return: The datetime object in 8601 string form.
      :rtype: datetime
      """
      datetime_obj = localize_datetime(datetime_obj, pytz.utc)
      if datetime_obj < MIN_DATE:
          datetime_obj = MIN_DATE
      elif datetime_obj > MAX_DATE:
          datetime_obj = MAX_DATE
      return datetime_obj.replace(tzinfo=None).strftime('%Y-%m-%dT%H:%M:%S.%f')[:-3] + 'Z'